Solar Terminator and Auroral Sources for Traveling Ionospheric Disturbances in the Midlatitude F Region

The occurrence of Traveling Ionospheric Disturbances (TIDs) at a midlatitude location (London, Canada, 43°N, 81°W) has been examined using data recorded by standard 5 min ionograms during the year 2000. It is found that the dominant source of TIDs during daytime appears to be the sunrise terminator but during nighttime the sunset terminator and magnetic disturbances both contribute to the TIDs. The daytime TIDs show a weak semiannual variation with maxima in solstices. The nighttime TIDs show insignificant annual variation.